Parasitic leiomyomas/fibroids are extra-uterine leiomyomas that present as benign peritoneal pelvic or abdominal smooth-muscle masses separate from the uterus.

Pathology

This leiomyoma likely originates as a pedunculated subserosal leiomyoma that twists and torses from its uterine pedicle. The contact with the uterus is then lost. Once free in the peritoneal cavity, it survives by recruiting neo-vascularization from adjacent structures. The originating pedunculated fibroid likely develops pre-menopausally, whereas the parasitic leiomyoma may become clinically evident before or after menopause ^ref.

This leiomyoma may also exist after surgery when small portions of the leiomyoma fall into the peritoneal cavity ^ref.

Occasionally, a broad ligament leiomyoma is also termed as a parasitic leiomyoma ⁴.

Classification

Parasitic leiomyomas are classified under the FIGO system as type 8 ⁵.

Radiographic features

On imaging, a parasitic leiomyoma presents as a solid pelvic or abdominal mass with characteristics similar to uterine leiomyoma ^ref. 

Treatment and prognosis

With behavior similar to uterine leiomyoma, a parasitic leiomyoma may recur after resection or, conversely, may show hormone-responsive behavior, including size stability or even shrinkage with natural, surgical, or chemical menopause ^ref. 

Surgery is usually performed for symptomatic relief or to prevent impingement of vital structures ^ref.

Differential diagnosis

The differential for a parasitic leiomyoma varies with its location and includes ^ref:

• ovarian stromal tumors

• leiomyosarcoma

• drop metastases

• lymphadenopathy 

See also

• disseminated peritoneal leiomyomatosis

• intravenous leiomyomatosis

• benign metastasizing leiomyoma